Blades for centrifugal fans and the like



. Sept. 17,1963 R. w. COWARI D 3,10 50 BLADES FOR CENTRIFUGAL FANS AND THE LIKE Filed Aug. 17,. 1960' Y i 2 Sheets- Sheet 1 I I I ,5 Is

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33 31 29 IO 4 1L INVENTOR. RicharJ W. Coward zaiiyi f v Rafterneys I Sept. 17, 1963 v R; w. COWARD 3, BLADES'FOR CENTRIFUGAL FANS AND THE LIKE Filed Aug. 17, 1960 2 Sheets-Sheet 2' INVENTOR. Richard W Coward WJQZW AM Rttorneys United States Patent 3,1(id,il5tl BLADES FGR CENTRIFUGAL FAN?) AND THE LIKE Richard W. Coward, Pd}. Box 1883, Birmingham, Ala. Filed Aug. 17, 1960, Ser. No. 5 3,195 4 Claims. (Cl. filth-128) This invention relates to blades for centrifugal fans and more particularly to blades in which a slot is provided so that abrasive particles in the gases being handled by the fan may pass therethrough.

Heretofore, in centrifugal fan blades having slots or openings therein such as the M. S. Leonard Patent No. 2,065,716 issued December 29, 1936, the slots have been of generally uniform area or size throughout their length. Slots of a uniform area of the type shown by Leonard have been found to be unsatisfactory as many of the abrasive particles in gases such as a stream of air tend to adhere to the portion of the blade directly adjacent the member supporting the blade which results in undue wear at the juncture of the blades with the supporting member.

By the present invention a centrifugal fan blade is provided having a pair of blade portions spaced to form a slot therebetween which increases in size from the supporting plate member to which the blades are secured. Thus, the greater the distance from the supporting member to which the blades are secured, the greater the size of the slot. I have discovered that the provision of a slot of this configuration causesv the abrasive particles striking the blade to pass through the slot substantially evenly across the width of the entire blade. This even distribution of the particles therefore prevents undue wear on the blade at any given point or area, as has been found to be the case with slots having a generally uniform sectional area throughout their length. The air stream with the abrasive particles therein coming in an eye of the fan normally is directed against the back supporting plate to which the blades are secured and moves therefrom along the blades. I have found that the slot of ever increasing size from the supporting member tends to equalize the air pressure along the width of the blades which results in the even distribution of abrasive particles throughout the width of the blades.

' There are several ways in which a slot of a progressively increasing size from the back plate member of a centrifugal fan may be obtained. One manner is to provide a pair of blade portions lying in parallel displaced planes with the adjacent edges of the blade portions defining the slot being spaced progressively farther apart from the supporting plate member to which the blade portions are secured. Another way is to displace the edges of the blade portions defining the slot out of parallel planes,

but with such edges more closely spaced near the inner end of the blade than at the outer end thereof thereby defining a slot which increases in size progressively from the supporting plate member. Next, the adjacent edges defining the slot may lie in parallel planes, if desired, and yet a slot of progressively increasing size from the supporting plate member may be provided as will be explained.

Apparatus embodying features of my invention is shown in the accompanying drawings, forming a part of this application, in which:

FIG. 1 is a front elevational view, partly in section, and with parts broken away showing a typical double inlet centrifugal fan embodying blades according to my invention;

FIG. 2 is. a fragmentary side elevational view of the impeller of the fan shown in FIG. 1 with a portion broken away to show the disposition of the blades on the impeller;

FIG. 3 is a fragmentary elevational view of a blade 2 shown in FIG. 2 comprising a pair of blade portions lying in parallel displaced planes and secured to the supporting plate member of the impeller while having a slot of progressively increasing size extending from the plate memher to which they are secured;

FIG. 4 is a fragmentary sectional View taken generally along the line 4-4 of FIG. 3; 4

FIG. 5 is a fragmentary, sectional view taken generally along the line 5-5 of FIG. 3 and showing how the slot of the blade of FIG. 3 increases in size adjacent the outer end of the blade;

FIG. 6 is a fragmentary, sectional view, of a modification of my invention showing the blade portions lying in non-parallel displaced planes and forming a slot therebetween of progressively increasing size from the supporting plate member;

FIG. 7 is a fragmentary, sectional view taken generally along the line 7-7 of FIG. 6;

FIG. 8 is a fragmentary, sectional view taken generally along the line 8-8 of FIG. 6 and showing how the slot of FIG. 6 increases in size adjacent the outer end of the blade;

FIG. 9 is a fragmentary, elevational view of a further modification of my invention in which the blade portions are disposed in non-parallel planes and with the edges arranged parallel to each other to form the ever increasing slot;

FIG. 10- is a fragmentary, sectional view taken generally along the line 10-41% of FIG. 9; and

FIG. 11 is a fragmentary, sectional View taken generally along the line 11-11 of FIG. 9.

Referring now to the drawings for a better understanding of my invention, and more particularly to FIG. l, I show a blower or centrifugal fan having a pair of inlet boxes it and 11 enclosed by a casing or housing 13 having a flange 15 to which air ducts (not shown) may be connected. Housing M covers an impeller indicated generally by the numeral 16. The fan discharge is indicated by numeral 17. Inlet vanes 18 and 19 are provided on opposite sides of impeller 16 at the eye of the fan. Impeller 16 is mounted on a shaft 21, in turn mounted in bearings 22 and 23 carried on pedestals 24.

Impeller 116 comprises a supporting plate member or center plate 26 secured to shaft 21 :and outer shroud rings 27 and 28 on opposite sides of the plate member. Hubs 29 and 31 are mounted on the shaft adjacent supporting plate 26. Between supporting plate 26 andv each of the shroud rings 27 and 28 are fan blades indicated generally by numeral 32. Cooling sleeves 33 surround shaft 21 with a relatively close clearance. Air from impeller 16 is directed along the shaft adjacent the inner surface of cooling sleeve 33. Cooling sleeves 33 are supported adjacent their inner ends by vanes 13 and 19 and at their outer ends by housing 13.

My invention comprises blades for use in a blower or centrifugal fan. such as described above in which the blade has a pair of blade portions defining a slot therebetween which progressively increases in size from the supporting plate member 26 of the blower.

Referring now to FIGS. 3-5 in which one form of the invention is shown, I show blade 32 as comprising inner and router blade portions 36 and 37, respectively, extending in parallel idisplaced planes and defining therebetween a slot 38 which increases in size outwardly from support-- ing member 26. A replaceable wear bar 39 is secured to the trailing surface of blade portion 37. Abrasive panti- Patented Sept. 1?, 1963 3 blade. Edges 41 and 42 of blade portions 37 and 36 preferably are sharpened as indicated. Edge 441 defines the outer edge of the slot and edge 42 defines the inner edge of slot 33 with edge 41 diverging from edge .2 with respect to the supporting member 26.

Since blade portions 36 and 37 lie in parallel but displaced planes, the distance D between the outer leading surface of blade portion 36 and the outer leading surface of blade portion 37 remains constant throughout the width of blade portions 36 and 37. By displacing blade portions 36 and 37, the leading surface of blade portion 37 is disposed forwardly of the leading surfaceof blade portion 36 so that particles moving along the leading surafce of blade portion 36 may be easily directed through slot 33. However, slot 38 is of progressively increasing size from supporting member 26 and the distance H between edge 41 of blade 37 and edge 42 of blade portion 36 increases progressively from plate 26 outwardly. FIGS. 3-5 therefore disclose one embodiment in which blade portions 36 and 37 are in displaced but parallel planes and yet have a slot therebetween of a progressively increasing size from the supporting member.

Referring now to FIGS. 6, 7 and 8 in which a further embodiment of my improved fan blade is shown, blade 32 comprises blade portions 36 and 37 lying in nonparallel planes and secured to supporting member 26 Wear bar 39 is mounted on the trailing side of blade portion 37 and the adjacent edges of blade portions 36 and 37- are indicated by the numerals 42 and 41, respcctively. A slot 38* is formed between blade portions 36 and 37 and is of a progressively increasing size from member 26. The outer leading surfaces of blade portions 36 and 37 are spaced progressively farther apart from member 26 as indicated by distance D. Distance D in FIG. 8 is greater than distance D in FIG. 7. Further, edges 41 and 42 are spaced progressively farther apart from each other as they extend from member 26 as indicated by the distance H. This is indicated by the fact that distance H in FIG. 7 is smaller than distance H in FIG. 8. Thus, slot 38 is of progressively increasing size from the supporting member 26.

Referring now to FIGS. 9, l0, and 11, an additional embodiment of my invention comprising blades having slots of a progressively increasing size therein is shown. Blade 32 comprises blade portions 37 and 36 having a slot 38 therebetween. Blade portions 36 and 37 are secured to supporting plate member 26* and a wear bar 39 is positioned on the trailing surface of blade portion 37 The edge of blade 37 defining slot 38 is indicated by the numeral 41' and the edge of blade portion 36 by 42. As shown in FIGS. and 11, the distance H, which indicates the distance between edges 41 and 42 in the plane of blade portion 36 is constant and does not change as blade portion 32 extends from plate 26 However, blade portions 36* and 37 extend in nonparallel displaced planes and the distance D from the leading surface of blade 36' to blade portion 37 is less in FIG. 10 than it is in FIG. 11. Thus, even though edges 41 and 42 are in parallel planes, slot 38 is of a progressively increasing size from supporting member 26 since blade portions 36 and 37 are in non-parallel planes.

From the foregoing, it is understood that I have provided a blade having a slot therein of a pro grcssively increasing size from the supporting member to which the blades are secured. Each of the embodiments shown discloses a slot between the blade portions of a progressively increasing size from the supporting member even though the blade portions may extend in parallel planes or even though the edges defining the slot may be parallel. In practice, instead of the abrasive particles channelling or maintaining a fixed path over the leading surfaces of the blades adjacent the supporting plate, they spread out across the width of the blades and flow through the slots 38, 38 or 38* in a very uniform manner. The wear occasioned by the presence of such particles therefore is 4 distributed evenly over my improved blade structure. By providing the replaceable Wear bars 39, 39 or 39', as the case may be, and locating them where the greatest wear occurs, I have effectively increased the life of the fan blades.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible to various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. In a centrifugal fan for gases containing abrasive material and having a central eye therein, a shaft mounted in bearings for rotation, 21 supporting member secured to said shaft for rotation therewith, a plurality of angularly spaced blades secured to said supporting member and extending outwardly from the face of the supporting member in a generally perpendicular relation, each of said blades having separate inner and outer blade portions with adjacent edges defining a slot therebetween, said edges diverging from each other relative to the supporting member in the plane in which the portions extend, the leading surface of said upper blade portion being disposed forwardly of the leading surface of said lower blade portion so that the abrasive particles moving along the surface of said lower blade portion are directed through the slot, and said slot increasing in area from the supporting member whereby patriclcs of abrasive material in the gases pass through the slot substantially uniformly throughout the length of the slot.

2. In a centrifugal fan for gases containing abrasive particles, a shaft mounted in bearings for rotation, a plurality of angularly spaced blades and a supporting plate member therefor mounted on said shaft for rotation therewith, each of said blades having a slot therein sloping outwardly with respect to the supporting plate member and the longitudinal axis of the shaft to permit abrasive material to pass through said slot, the leading surface of the blade outwardly of the slot being displaced forwardly of the leading surface of the blade inwardly of the slot, and the edge of said blade defining the outer edge of said slot diverging from the edge of the blade defining the inner edge of the slot with respect to the supporting member and in a plane parallel to the plane in which the blades extend whereby abrasive particles moving from the center of the fan are directed through said slot in a substantially uniform manner throughout the length of the slot.

3. In a centrifugal fan for gases containing abrasive particles, a shaft mounted in bearings for rotation, a supporting plate member mounted on said shaft for rotation therewith and extending generally perpendicular to the axis of the shaft, 21 shroud ring spaced from said plate member, a plurality of angularly spaced blades secured to and extending between the shroud ring and the supporting plate member, each of said blades having a pair of separate blade portions spaced to form a slot therebetween extending generally parallel to the longitudinal axis of the shaft, the leading surface of the blade portion outwardly of the slot being displaced forwardly of the leading surface of the blade portion inwardly of the slot so that particles may be easily directed through said slot, and the blade portions being spaced progressively farther apart from the supporting plate member to form an ever increasing slot whereby particles of abrasive material in the gases pass through the slot substantially uniformly throughout the length of the slot and the width of the blade portions.

4. In a double inlet centrifugal fan for gases containing abrasive particles, a shaft mounted in bearings for rotation, a center supporting plate member mounted on said shaft for rotation therewith and extending generally perpendicular to the longitudinal axis of the shaft, a shroud ring on each side of said center plate member and forming an eye for each end of the fan through which air containing abna'sive material passes, 'a plurality of angul-arly spaced blades extending between and secured to each shroud ring and the center plate member therebetween, each of said blades having sepanate inner and outer blade portions spaced to form a slot therebetween, the adjacent surfiaces forming the slot sloping outwardly from the supporting plate member and the outer blade portion being displaced fiorwardly of the inner blade portion whereby particles moving along said inner blade portion pass through said slot, and the blade pontions defining the slot being spaced progressively farther apart them an end of the slot nearest the center plate so that the slot increases in size as it extends from the center plate and abmasive particles in the gases pass through the slot substantially uniformly throughout the length of the slot.

References Cited in the file of this patent UNITED STATES PATENTS Hurst Aug. 6, Exton Jan. 13, Von Karman et a1. Mar. 29, Leonard Dec. 29, Ooward July 24, Warner Jan. 14, Busquet 21,

FOREIGN PATENTS Great Britain Aug. 13, Fnance Sept. 23, France Nov. 4, 

1. IN A CENTRIFUGAL FAN FOR GASES CONTAINING ABRASIVE MATERIAL AND HAVING A CENTRAL EYE THEREIN, A SHAFT MOUNTED IN BEARINGS FOR ROTATION, A SUPPORTING MEMBER SECURED TO SAID SHAFT FOR ROTATION THEREWITH, A PLURALITY OF ANGULARLY SPACED BLADES SECURED TO SAID SUPPORTING MEMBER AND EXTENDING OUTWARDLY FROM THE FACE OF THE SUPPORTING MEMBER IN A GENERALLY PERPENDICULAR RELATION, EACH OF SAID BLADES HAVING SEPARATE INNER AND OUTER BLADE PORTIONS WITH ADJACENT EDGES DEFINING A SLOT THEREBETWEEN, SAID EDGES DIVERGING FROM EACH OTHER RELATIVE TO THE SUPPORTING MEMBER IN THE PLANE IN WHICH THE PORTIONS EXTEND, THE LEADING SURFACE OF SAID UPPER BLADE PORTION BEING DISPOSED FORWARDLY OF THE LEADING SURFACE OF SAID LOWER BLADE PORTION SO THAT THE ABRASIVE PARTICLES MOVING ALONG THE SURFACE OF SAID LOWER BLADE PORTION ARE DIRECTED THROUGH THE SLOT, AND SAID SLOT INCREASING IN AREA FROM THE SUPPORTING MEMBER WHEREBY PATRICLES OF ABRASIVE MATERIAL IN THE GASES PASS THROUGH THE SLOT SUBSTANTIALLY UNIFORMLY THROUGHOUT THE LENGTH OF THE SLOT. 